The present invention relates to a driving apparatus for vehicle, having an electric motor as a prime driving source (mover) for driving drive wheels.
An electric vehicle employs the electric motor, namely, a motor as a prime mover, and a hybrid vehicle is one employing the electric motor and an internal combustion engine as a prime mover. In such a vehicle equipped with the electric motor as the prime mover, there are employed a driving apparatus, which is provided with: an electric motor; a speed reduction mechanism for reducing speeds of its rotor shaft; and a differential gear unit, namely, a differential mechanism, for absorbing the difference in rotation between left and right drive wheels in turning the vehicle. The electric motor, the speed reduction mechanism and the differential gear unit are incorporated in a case, so that power of the electric motor is transmitted to the drive wheels through a drive shaft coupling the differential gear unit and the left and right drive wheels.
Examples of the driving apparatus used in the electric vehicle are disclosed in Japanese Patent Laid-open Nos. 10-278603 and 11-98616. The driving apparatus comprises: a rotor shaft concentric with a rotor of an electric motor; a reduction shaft provided with a first speed reduction gear train between this rotor shaft and another rotor shaft disposed in parallel thereto; and a differential gear unit provided with a final reduction driven gear, which is engaged with a final reduction drive gear fixed to the reduction shaft. The driving apparatus is therefore formed into a parallel three-shaft structure in which an axle shaft, the rotor shaft, and the reduction shaft are parallel to one another, the axle shaft being fixed to a bevel gear of the differential gear unit and coupled to a drive shaft.